The present invention generally relates to a thermosensitive recording material, and more particularly to a diazo-type thermosensitive recording material capable of fixing images by light exposure. In the thermosensitive recording material according to the present invention, image formation is done by a thermal head which is heated to a predetermined temperature. The thermosensitive recording material which bears the thus formed images is exposed to light. By this exposure, the non-image area, that is, the background of the thermosensitive recording material, loses its thermosensitivity, and no image can be formed any longer even if heat is applied thereto later on, whereby the images formed on the thermosensitive recording material can be fixed permanently.
Conventionally, thermosensitive recording materials are used as copying materials for books or documents; output recording sheets for computers, facsimile apparatus and medical analytical instruments; thermosensitive-recording-type magnetic tickets; and thermosensitive-recording-type labels.
Because of the ease of automatic recording with thermosensitive recording materials, it would be advantageous to use thermosensitive recording materials for preparing securities, merchandise coupons, entrance tickets, certificates, payment slips and the like. However, in these fields, high recording reliability is required. In other words, it is required that the recorded images be capable of being made permanent and that it be impossible to record additions to the already recorded information, and, thus, that recorded matter on such thermosensitive recording materials not be alterable. Otherwise, reliability of the record cannot be obtained.
Conventionally, as an image-fixable thermosensitive recording material, a diazo-type thermosensitive recording material is known, which utilizes the coloring reaction between a diazo compound and a coupler.
However, the conventional diazo-type thermosensitive recording material cannot be used in practice because of (1) slow thermal response when a thermal head is employed, and (2) poor preservability of the material itself and of the images formed thereon.
Recently, a thermosensitive recording material has been sought which would allow rapid recording in facsimile apparatus, computers and medical analytical instruments. Especially in the field of facsimiles, a thermosensitive recording material suitable for rapid recording is required so that communication costs can be minimized.